Range

The range of a function $f:A\to B$ is the subset of $B$ given as $\{f(a)\mid a\in A\}$, i.e., the set of elements of $B$ that arise as outputs of the function.

Examples: Given $f:A\to B$ so that for every $x\in A:f=x^2$ in this case the range is a subset of $B$ encompassing all its positive real numbers.